Debris basin policy and design

Debris flows cause considerable property damage and loss of life. The debris basin is a widely used control alternative, for which accurate design methods are not available. Thus, there is a need for a systematic design procedure, as well as a practical basis for establishing policy elements. A design procedure that accounts for seasonal volumes of debris is presented. The choice of the design return period and burn interval, both of which are important policy elements, is a function of the hazard level associated with failure. The monitoring and maintenance of debris basins are also important policy elements. The frequency of monitoring a basin to ensure adequate storage is a function of the potential hazard presented by a debris flow to the area downstream of the basin, as well as the precipitation, the frequency of burning in the watershed, and the drainage area. A procedure for estimating the temporal accumulation of debris is presented so that public agencies will know when to monitor and dredge each debris basin in their jurisdiction. The adoption of rational design methods and policy elements relating to debris basins should minimize the risk of failure of the basins.